Preparation method and application of hard carbon negative electrode material for sodium ion battery

Abstract

The invention relates to the technical field of sodium-ion batteries, in particular to a preparation method and application of a hard carbon negative electrode material for a sodium-ion battery, and aims to improve the specific capacity of a hard carbon negative electrode. According to the method, the graphite microcrystal domain and interlayer spacing are controllably adjusted mainly through an oil bath pre-carbonization method, and active storage sites of sodium ions in hard carbon are effectively increased.

Description

[Technical field]

[0001] The present invention belongs to the technical field of sodium ion batteries, and in particular relates to a preparation method and application of a hard carbon negative electrode material for a sodium ion battery. [Background technology]

[0002] Lithium-ion batteries have been commercialized for 30 years and have formed a mature industrial scale. They have shown excellent performance in energy storage fields such as portable electronic devices and power batteries such as electric vehicles. With the continuous development of fast energy storage technology, the requirements for energy storage systems are also increasing, so lithium-ion batteries are developing rapidly. However, the limited lithium resources in the world have become an obstacle to the continued development of lithium-ion batteries. Therefore, people have turned their attention to sodium-ion batteries, which are also alkali metals. Sodium resources are abundant in the world, and their solvation energy is lower than that of lithium ions, which has obvious advantages.

[0003] The negative electrode material is a key part of the sodium ion battery. Due to the large radius of sodium ions, graphite, which was originally suitable for the negative electrode of lithium ion batteries, is not competent for the negative electrode of sodium ion batteries. Therefore, hard carbon with an interlayer spacing larger than graphite has been discovered. It has a stable structure, low cost and controllable morphology, and is a promising negative electrode material for sodium ion batteries.

[0004] At present, it is still difficult to obtain hard carbon negative electrode materials with excellent sodium storage performance under the constraint of low production cost, which limits the application of hard carbon negative electrode materials in sodium ion batteries. [Summary of the invention]

[0005] In view of the above, it is necessary to provide a method for preparing a hard carbon negative electrode material for a sodium ion battery and its application, mainly through an oil bath pre-carbonization method, which can controllably adjust the length of its graphite microcrystalline domains and pseudo-graphite domains, effectively increasing the active storage sites of sodium ions in the hard carbon.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A method for preparing a hard carbon negative electrode material for a sodium ion battery, the method comprising the following steps:

[0008] S1: Mix the sugar and silicone oil in a conical flask, stir evenly to obtain a mixed material, and set aside;

[0009] S2: placing the conical flask containing the mixed material in an oil bath, heating it to a certain temperature and then keeping it warm for 2-4 hours to obtain a pre-carbonized precursor for standby use;

[0010] S3: washing the pre-carbonized precursor obtained in step S2 to obtain a washed material for standby use;

[0011] S4: Grinding the washed material in step S3 to obtain fine particles for later use;

[0012] S5: In an inert atmosphere, the fine particles obtained after grinding are carbonized to obtain the hard carbon negative electrode material.

[0013] In the present invention, further, the sugar in step S1 is selected from one of glucose, fructose, galactose, ribose, xylose or sucrose, or any combination thereof.

[0014] In the present invention, further, the organic silicone oil in step S1 is selected from any one of methyl silicone oil, dimethyl silicone oil, phenyl silicone oil and methylphenyl silicone oil.

[0015] In the present invention, further, in step S1, the material-liquid ratio of the sugar and the silicone oil is 3g:10ml.

[0016] In the present invention, further, the certain temperature of heating in step S2 is 220-280°C.

[0017] In the present invention, further, the washing of S3 is performed by alternately washing with ethanol and deionized water and then filtering, and then drying in a blast oven at 100° C. for 12 hours.

[0018] In the present invention, further, the mesh size of the S3 particles is 300 meshes.

[0019] In the present invention, further, the temperature for carbonizing the S5 is 1200° C. and the holding time is 2 h.

[0020] In the present invention, further, the inert gas in step S5 is selected from any one of nitrogen, helium and argon.

[0021] The present invention also provides an application of a hard carbon negative electrode material for a sodium ion battery prepared by the method described above. The hard carbon negative electrode material for a sodium ion battery is used in the preparation of a sodium ion battery. The obtained hard carbon negative electrode material has a larger interlayer spacing, which prevents the collapse of the pseudo-graphite domain structure during the sodium ion deintercalation process, and is beneficial to the capacity retention rate of the material in a long cycle. In addition, a larger interlayer spacing increases the storage of sodium ions in the hard carbon material, thereby promoting an increase in specific capacity.

[0022] The present invention has the following beneficial effects:

[0023] The present invention proposes a method for preparing a hard carbon negative electrode material for a sodium ion battery, and applies the hard carbon negative electrode material prepared by the method to the preparation of a sodium ion battery. The method of the present application solves the problems of low specific capacity, unstable source, high cost, etc. of existing hard carbon negative electrode materials. A simple pre-carbonization method for hard carbon materials is proposed to improve the specific capacity of the hard carbon negative electrode. In the preparation process, the length of its graphite microcrystalline domain and pseudo-graphite domain is controllably adjusted by a pre-carbonization method in an oil bath, which effectively increases the active storage sites of sodium ions in the hard carbon. The sodium ion battery prepared by the hard carbon negative electrode material obtained by the method still maintains a high specific capacity after 50 discharges, and has a very broad application prospect.

Brief Description of the Drawings

[0024] Figure 1 is a SEM image of the hard carbon negative electrode material prepared in Example 7 of the present invention;

[0025] Figure 2 is a SEM image of the hard carbon negative electrode material prepared in Comparative Example 1;

[0026] Figure 3 is a SEM image of the hard carbon negative electrode material prepared in Comparative Example 2;

[0027] Figure 4 is an XRD comparison diagram of the hard carbon negative electrode materials prepared in Example 7 of the present invention and Comparative Examples 1-2;

[0028] Figure 5 It is a comparison chart of the charge and discharge curves of the hard carbon negative electrode materials prepared in Example 7 of the present invention and Comparative Examples 1-2. [Specific implementation method]

[0029] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific implementation disclosed below.

[0030] Embodiment 1:

[0031] This embodiment provides a method for preparing a hard carbon negative electrode material for a sodium ion battery, and the steps are as follows:

[0032] S1: Dissolve 15g of glucose in 50ml of dimethyl silicone oil, put them into a conical flask and stir them evenly to obtain a mixed material for later use;

[0033] S2: placing the conical flask containing the mixed material in an oil bath, gradually heating it to 220° C. in the oil bath and then keeping it warm for 3 hours, and naturally cooling it to room temperature after the end of the insulation to obtain a pre-carbonized precursor for standby use;

[0034] S3: washing the pre-carbonized precursor obtained in step S2, specifically washing with ethanol and deionized water alternately, and finally filtering, and then drying in a blast oven at 100° C. for 12 hours to obtain a washed material for standby use;

[0035] S4: Grind the washed material in step S3 to obtain 300-mesh particles for later use;

[0036] S5: Place the finely crushed particles in a tubular furnace, introduce argon gas, raise the temperature to 1200° C., and keep the temperature for 2 hours to obtain a carbon negative electrode material for a sodium ion battery.

[0037] Embodiment 2:

[0038] This embodiment provides a method for preparing a hard carbon negative electrode material for a sodium ion battery, and the steps are as follows:

[0039] S1: Dissolve 15g of glucose in 50ml of dimethyl silicone oil, put them into a conical flask and stir them evenly to obtain a mixed material for later use;

[0040] S2: placing the conical flask containing the mixed material in an oil bath, gradually heating it to 230° C. in the oil bath and then keeping it warm for 3 hours, and naturally cooling it to room temperature after the end of the insulation to obtain a pre-carbonized precursor for standby use;

[0041] S3: washing the pre-carbonized precursor obtained in step S2, specifically washing with ethanol and deionized water alternately, and finally filtering, and then drying in a blast oven at 100° C. for 12 hours to obtain a washed material for standby use;

[0042] S4: Grind the washed material in step S3 to obtain 300-mesh particles for later use;

[0043] S5: The finely crushed particles are placed in a tubular furnace for carbonization, argon gas is introduced, the temperature is raised to 1200° C., and the heat preservation time is 2 hours to obtain a carbon negative electrode material for a sodium ion battery.

[0044] Embodiment 3:

[0045] This embodiment provides a method for preparing a hard carbon negative electrode material for a sodium ion battery, and the steps are as follows:

[0046] S1: Dissolve 15g of glucose in 50ml of dimethyl silicone oil, put them into a conical flask and stir them evenly to obtain a mixed material for later use;

[0047] S2: placing the conical flask containing the mixed material in an oil bath, gradually heating it to 240° C. in the oil bath and then keeping it warm for 3 hours, and naturally cooling it to room temperature after the end of the insulation to obtain a pre-carbonized precursor for standby use;

[0048] S3: washing the pre-carbonized precursor obtained in step S2, specifically washing with ethanol and deionized water alternately, and finally filtering, and then drying in a blast oven at 100° C. for 12 hours to obtain a washed material for standby use;

[0049] S4: Grind the washed material in step S3 to obtain 300-mesh particles for later use;

[0050] S5: The finely crushed particles are placed in a tubular furnace for carbonization, argon gas is introduced, the temperature is raised to 1200° C., and the heat preservation time is 2 hours to obtain a carbon negative electrode material for a sodium ion battery.

[0051] Embodiment 4:

[0052] This embodiment provides a method for preparing a hard carbon negative electrode material for a sodium ion battery, and the steps are as follows:

[0053] S1: Dissolve 15g of glucose in 50ml of dimethyl silicone oil, put them into a conical flask and stir them evenly to obtain a mixed material for later use;

[0054] S2: placing the conical flask containing the mixed material in an oil bath, gradually heating it to 250° C. in the oil bath and then keeping it warm for 3 hours, and naturally cooling it to room temperature after the end of the insulation to obtain a pre-carbonized precursor for standby use;

[0055] S3: washing the pre-carbonized precursor obtained in step S2, specifically washing with ethanol and deionized water alternately, and finally filtering, and then drying in a blast oven at 100° C. for 12 hours to obtain a washed material for standby use;

[0056] S4: Grind the washed material in step S3 to obtain 300-mesh particles for later use;

[0057] S5: The finely crushed particles are placed in a tubular furnace for carbonization, argon gas is introduced, the temperature is raised to 1200° C., and the heat preservation time is 2 hours to obtain a carbon negative electrode material for a sodium ion battery.

[0058] Embodiment 5:

[0059] This embodiment provides a method for preparing a hard carbon negative electrode material for a sodium ion battery, and the steps are as follows:

[0060] S1: Dissolve 15g of glucose in 50ml of dimethyl silicone oil, put them into a conical flask and stir them evenly to obtain a mixed material for later use;

[0061] S2: placing the conical flask containing the mixed material in an oil bath, gradually heating it to 260° C. in the oil bath and then keeping it warm for 3 hours, and naturally cooling it to room temperature after the end of the insulation to obtain a pre-carbonized precursor for standby use;

[0062] S3: washing the pre-carbonized precursor obtained in step S2, specifically washing with ethanol and deionized water alternately, and finally filtering, and then drying in a blast oven at 100° C. for 12 hours to obtain a washed material for standby use;

[0063] S4: Grind the washed material in step S3 to obtain 300-mesh particles for later use;

[0064] S5: The finely crushed particles are placed in a tubular furnace for carbonization, argon gas is introduced, the temperature is raised to 1200° C., and the heat preservation time is 2 hours to obtain a carbon negative electrode material for a sodium ion battery.

[0065] Embodiment 6:

[0066] This embodiment provides a method for preparing a hard carbon negative electrode material for a sodium ion battery, and the steps are as follows:

[0067] S1: Dissolve 15g of glucose in 50ml of dimethyl silicone oil, put them into a conical flask and stir them evenly to obtain a mixed material for later use;

[0068] S2: placing the conical flask containing the mixed material in an oil bath, gradually heating it to 270° C. in the oil bath and then keeping it warm for 3 hours, and naturally cooling it to room temperature after the end of the insulation to obtain a pre-carbonized precursor for standby use;

[0069] S3: washing the pre-carbonized precursor obtained in step S2, specifically washing with ethanol and deionized water alternately, and finally filtering, and then drying in a blast oven at 100° C. for 12 hours to obtain a washed material for standby use;

[0070] S4: Grind the washed material in step S3 to obtain 300-mesh particles for later use;

[0071] S5: The finely crushed particles are placed in a tubular furnace for carbonization, argon gas is introduced, the temperature is raised to 1200° C., and the heat preservation time is 2 hours to obtain a carbon negative electrode material for a sodium ion battery.

[0072] Embodiment 7:

[0073] This embodiment provides a method for preparing a hard carbon negative electrode material for a sodium ion battery, and the steps are as follows:

[0074] S1: Dissolve 15g of glucose in 50ml of dimethyl silicone oil, put them into a conical flask and stir them evenly to obtain a mixed material for later use;

[0075] S2: placing the conical flask containing the mixed material in an oil bath, gradually heating it to 280° C. in the oil bath and then keeping it warm for 3 hours, and naturally cooling it to room temperature after the end of the insulation to obtain a pre-carbonized precursor for standby use;

[0076] S3: washing the pre-carbonized precursor obtained in step S2, specifically washing with ethanol and deionized water alternately, and finally filtering, and then drying in a blast oven at 100° C. for 12 hours to obtain a washed material for standby use;

[0077] S4: Grind the washed material in step S3 to obtain 300-mesh particles for later use;

[0078] S5: The finely crushed particles are placed in a tubular furnace for carbonization, argon gas is introduced, the temperature is raised to 1200° C., and the heat preservation time is 2 hours to obtain a carbon negative electrode material for a sodium ion battery.

[0079] Comparative Example 1:

[0080] The preparation scheme of this comparative example is the same as that of the above-mentioned Example 7, with the only difference being that, in this comparative example, the glucose is not pre-carbonized in an oil bath, but the glucose is directly placed in a tubular furnace, the precursor carbon is placed in a tubular furnace, argon gas is introduced, the temperature is raised to 1200°C, and the heat preservation time is 2h to obtain a carbon negative electrode material for a sodium ion battery.

[0081] Comparative Example 2:

[0082] The preparation method of the hard carbon negative electrode material of this comparative example comprises the following steps:

[0083] Step (1): Dissolve 5 g of glucose in 40 ml of deionized water, stir thoroughly to dissolve, then put it into a 100 mL high pressure hydrothermal reaction kettle, and finally place the hydrothermal kettle in a forced air oven and heat it at 180° C. for 12 h.

[0084] Step (2): placing the hydrothermal precursor carbon in a tubular furnace, introducing argon gas, heating to 1200° C., and keeping the temperature for 2 h to obtain a carbon negative electrode material for a sodium ion battery.

[0085] In Examples 1-7, oligosaccharides and highly reactive molecules were produced after the glucose was bathed in oil, and glycosylation reaction occurred at the same time, in which cheap intermediates were produced. However, in Comparative Example 1, the untreated glucose was directly carbonized at high temperature, and the above process did not occur.

[0086] The sodium ion battery hard carbon negative electrode materials prepared in Examples 1-7 and Comparative Examples 1-2 were used to prepare sodium ion battery negative electrode sheets, and button batteries were assembled and tested at a current density of 100 mA / g and a voltage range of 0.001-2.0 V. The results are shown in Table 1.

[0087] Table 1

[0088]

[0089]

[0090] In addition, the SEM image of the hard carbon negative electrode material of Example 7 is as follows Figure 1 As shown in the figure, the hard carbon is in the form of uniformly distributed small irregular blocks. The SEM image of the hard carbon negative electrode material of Comparative Example 1 is as follows Figure 2 As shown, it presents an irregular block shape. The SEM image of the hard carbon negative electrode material of Comparative Example 2 is as follows Figure 3 As described above, the figure shows agglomerated hard carbon microspheres, combined with Figure 1-3 It can be seen that the uniformly distributed small block-shaped hard carbon is beneficial to the improvement of specific capacity.

[0091] The XRD comparison diagrams of the hard carbon negative electrode materials prepared in Example 7 and Comparative Examples 1-2 are shown in FIG. Figure 4 As shown, from Figure 4 It can be seen that the peak representing the 002 crystal plane in the comparative example is near 23.8°, while the peak representing the 002 crystal plane in the embodiment is near 21.6°. According to the Bragg equation 2dsinθ=nλ, the embodiment has the largest interlayer spacing, which is conducive to the deintercalation of sodium ions.

[0092] The comparison of the charge and discharge curves of the second cycle of the hard carbon negative electrode material prepared in Example 7 and Comparative Example 1-2 is shown in the figure Figure 5 As shown, from Figure 5 It can be seen that the embodiment has a high specific capacity of up to 400 mAh / g, while the specific capacity of comparative example 1 is only 140 mAh / g.

[0093] The negative electrode material prepared by the method of the present application is used in the preparation of sodium ion batteries. The obtained hard carbon negative electrode material has a larger interlayer spacing, which prevents the collapse of the pseudo-graphite domain structure during the sodium ion extraction and insertion process, which is beneficial to the capacity retention rate of the material in a long cycle. In addition, the larger interlayer spacing increases the storage of sodium ions in the hard carbon material, which promotes the improvement of specific capacity.

[0094] The above-mentioned embodiments merely express several implementation modes of the present invention, and the description thereof is relatively specific and detailed, but it should not be understood as limiting the scope of the present invention.

Claims

1. A method for preparing a hard carbon negative electrode material for a sodium ion battery, characterized in that: The method comprises the following steps: S1: Mix the sugar and silicone oil in a conical flask, stir evenly to obtain a mixed material, and set aside; S2: placing the conical flask containing the mixed material in an oil bath, heating it to a certain temperature and then keeping it warm for 2-4 hours to obtain a pre-carbonized precursor for standby use; S3: washing the pre-carbonized precursor obtained in step S2 to obtain a washed material for standby use; S4: Grinding the washed material in step S3 to obtain fine particles for later use; S5: In an inert atmosphere, the fine particles obtained after grinding are carbonized to obtain the hard carbon negative electrode material.

2. The method according to claim 1, characterized in that The sugar in step S1 is selected from one of glucose, fructose, galactose, ribose, xylose or sucrose, or any combination thereof.

3. The method according to claim 1, characterized in that The organic silicone oil in step S1 is selected from any one of methyl silicone oil, dimethyl silicone oil, phenyl silicone oil and methylphenyl silicone oil.

4. The method according to claim 1, characterized in that The material-liquid ratio of the sugar to the silicone oil in step S1 is 3 g:10 ml.

5. The method according to claim 1, characterized in that The certain temperature to be heated in step S2 is 220-280°C.

6. The method according to claim 1, characterized in that The S3 is washed by alternately washing with ethanol and deionized water and then filtered, and then dried in a forced air oven at 100° C. for 12 hours.

7. The method according to claim 1, characterized in that The mesh size of the finely crushed particles of S3 is 300 meshes.

8. The method according to claim 1, characterized in that The temperature at which the S5 is carbonized is 1200°C.

9. The method according to claim 1, characterized in that: The inert gas in step S5 is selected from any one of nitrogen, helium and argon.

10. Application of the hard carbon negative electrode material for sodium ion battery prepared by the method according to claims 1-9, characterized in that: The hard carbon negative electrode material for sodium ion batteries is used in the preparation of sodium ion batteries.

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